ASVAB Mechanical Comprehension Practice Test 147421 Results

Your Results Global Average
Questions 5 5
Correct 0 3.24
Score 0% 65%

Review

1

Which of these is the formula for force?

77% Answer Correctly

F = a/m

F = am2

F = ma

F = m/a
Solution

Newton's Second Law of Motion states that "The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object." This Law describes the linear relationship between mass and acceleration when it comes to force and leads to the formula F = ma or force equals mass multiplied by rate of acceleration.

2 The green box weighs 40 lbs. and a 15 lbs. weight is placed 5 ft. from the fulcrum at the blue arrow. How far from the fulcrum would the green box need to be placed to balance the lever?
57% Answer Correctly
7.5 ft.
0.47 ft.
1.88 ft.
8 ft.
Solution

To balance this lever the torques on each side of the fulcrum must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:

Rada = Rbdb

where a represents the left side of the fulcrum and b the right, R is resistance (weight) and d is the distance from the fulcrum.

Solving for da, our missing value, and plugging in our variables yields:

da = \( \frac{R_bd_b}{R_a} \) = \( \frac{15 lbs. \times 5 ft.}{40 lbs.} \) = \( \frac{75 ft⋅lb}{40 lbs.} \) = 1.88 ft.

3 A = 7 ft., the green box weighs 35 lbs., and the blue box weighs 75 lbs. What does distance B need to be for this lever to balance?
65% Answer Correctly
10 ft.
3.27 ft.
1.09 ft.
9.8 ft.
Solution
In order for this lever to balance, the torque acting on side A must equal the torque acting on side B. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB

For this problem, the equation becomes:

35 lbs. x 7 ft. = 75 lbs. x dB

dB = \( \frac{35 \times 7 ft⋅lb}{75 lbs.} \) = \( \frac{245 ft⋅lb}{75 lbs.} \) = 3.27 ft.

4

Collinear forces:

73% Answer Correctly

act along the same line of action

pass through a common point

act in a common plane

are unrelated to each other
Solution

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

5 If A = 10 ft., B = 1 ft., C = 5 ft., the green box weighs 30 lbs. and the blue box weighs 45 lbs., what does the orange box have to weigh for this lever to balance?
44% Answer Correctly
300 lbs.
25.5 lbs.
51 lbs.
17 lbs.
Solution
In order for this lever to balance, the torque acting on each side of the fulrum must be equal. So, the torque produced by A must equal the torque produced by B and C. Torque is weight x distance from the fulcrum which means that the following must be true for the lever to balance:

fAdA = fBdB + fCdC

For this problem, this equation becomes:

30 lbs. x 10 ft. = 45 lbs. x 1 ft. + fC x 5 ft.

300 ft. lbs. = 45 ft. lbs. + fC x 5 ft.

fC = \( \frac{300 ft. lbs. - 45 ft. lbs.}{5 ft.} \) = \( \frac{255 ft. lbs.}{5 ft.} \) = 51 lbs.